The present invention relates to a planting or seedling flat and more particularly to such a flat having a multiplicity of planting cells providing open upper ends adapted to receive growing medium, seeds, water, fertilizer, and the like; downwardly constricted closed lower ends defining reservoirs for the retention of residual water, fertilizer, and the like accessible to the roots of the plants grown in the cells; and aerating openings disposed above the reservoirs serving the combined purposes of supplying air to the growing medium and providing drainage of water and fertilizer in excess of an amount sufficient to fill the reservoirs.
Planting flats are employed for growing plants from seeds or cuttings. When such plants have reached a given stage of growth, they are taken from such flats and planted in other containers or in open fields. What once was entirely a manual operation of filling such flats with soil or other growing medium, planting the seeds or cuttings, and hand watering the soil has become a highly mechanized procedure. Many field crops, such as tomatoes, are first planted in flats and grown in greenhouses before being transplanted to the open field. In areas in which late frosts are a problem, this procedure permits the farmer to achieve plants of a significant size by the time it is safe to plant them outside and thus prior to exposing them to the hazards of frost, mechanical damage, preditory insects, caterpillars, and the like encountered in the field.
The growing season for plants in flats is usually quite brief. Such plants are required in great numbers at one time, orders for such plants frequently being for millions of the plants at a time. The plants must be healthy, uniform, weed-free and economical. They should be as vigorous and stalky as circumstances permit. They should receive as little root damage as possible during transplanting and must be economical. The saving of even a cent a flat, or one plant per hundred, is a significant saving in commercial operations.
Machines have been developed which accept flats having a multiplicity of receptacles therein, fill the receptacles with disinfected soil or other growing medium, place one seed in each receptacle, cover the seeds, and compact the soil. Such machines have been of great benefit to the industry but the planting flats themselves have suffered from many difficulties which have inspired the present invention.
Prior to the present invention, it has been erroneously believed in the industry that the planting cells of flats must have drainage openings to avoid an objectionable accumulation of salts, over watering, stagnation, or souring. Such openings can be typified by those shown at 34 and 58 in U.S. Pat. No. 3,667,159, at c in U.S. Pat. No. 2,045,189, and at 3 in British Pat. No. 1,034,256. Thus, such drainage openings have been uniformally utilized even though recognized to cause serious troubles. They permit roots to grow downwardly and out through the openings. Such roots are broken off when the plants are removed from the flats thus frequently impairing their survival, aggravating the shock of transplanting, or at least impairing the plants' rate of growth. Further, such drainage openings have been recognized as permitting the rapid escape of irrigation water resulting in the leaching of nutrients from the soil and a requirement for excessively frequent irrigation and fertilization.
The present invention resides in the discovery that drainage openings in the lower ends of planting cells in flats are not only unnecessary but are undesirable.
The invention further resides in the discovery that if such drainage openings are moved upwardly from the lower ends of such planting cells so that the cells have imperforate lower end portions constituting reservoirs beneath such openings a great many advantages accrue. The openings become ventilation openings conducive to superior plant growth. The reservoirs accumulate residual water reducing the frequence of required irrigation. The reservoirs serve to retain fertilizer and other plant nutrient materials in position conveniently accessible to the roots of the growing plants rather than having them leached directly from the soil. Plants grown in such cells are markedly sturdier and stalkier.
Still further, the invention resides in forming such reservoirs so as to have substantially conical lower end portions terminating in hemispherical lower ends which facilitate plant and root mass removal as well as shaping such root masses for more advantageous growth when planted in a field. As the roots of the plant grow downwardly, they are confined so as to form highly desirable root masses or balls. Such plants and root masses with entrapped soil are pulled from such cells, they are much more easily released from the flats. In actual practice, tomato plants only one and one-half to two inches high, two or three weeks after planting, can readily be pulled from the plant cells of the flats of the present invention together with their growing medium while normally such tomato plants need to be about six weeks old and eight or ten inches tall in order to permit satisfactory removal. Two factors are principally involved. There are no bottom drainage openings through which the roots can grow and they make no effort to extend through the elevated drainage or ventilation openings. The protracted presence of water in the reservoir better lubricates the root masses in a wick-like action for extraction from the cells. Additionally, the confined and shaped root masses more quickly become established when transplanted so as to minimize shock and insure growing continuity.